Geographic Range

American avocets are found in western North America from March through October and in coastal California, southern Texas, Florida, Louisiana and south to Guatemala in winter. (Gill, 1995; Soothill and Soothill, 1982)

Physical Description

Graceful and sleek, these long-legged waders have a black bill and light blue legs. Avocets are the tallest and longest-legged birds in their family. They are 400 to 500 mm in length and have a wingspan of 213 to 242 mm. They are often confused with black-necked stilts (Himantopus mexicanus), but are distinguishable by the bold black and white pattern on their back and wings and a strongly upcurved black bill. Females are similar in appearance to males but with a shorter and more upwardly-curved bill, male bills are longer and straighter. They are the only avocet with distinct breeding and non-breeding plumages. Breeding plumage is obtained in the first year and is a beautiful rusty cinnamon along the head and neck. Basic plumage is a gray head. Adult breeding plumage appears from January to March and is lost in July to September. (Hayman, et al., 1986; Kaufman, 2000; Soothill and Soothill, 1982)

Development

1 brood per year, usually 3-5 eggs laid which are a pale ashy-yellow or olive-brown covered evenly with dark brown spots and blotches. Eggs are laid at intervals of 1-2 days, with a full clutch in 5 days (Hayman et al., 1986; Soothill & Soothill, 1982; Nethersole-Thompson, 1986).

Breeding occurs between April and June. Nests are built on shore and are usually scrapes in the ground; they are sometimes lined with dry grass or mud chips. The female lays 3 to 5 eggs (4 on average); eggs are olive colored with brown and black spots. Incubation lasts 22 to 29 days and the eggs hatch synchronously. Fledging occurs after 28 to 35 days. (Ehrlich, et al., 1988; Hayman, et al., 1986; Soothill and Soothill, 1982)

Both male and female American avocets incubate the eggs. Incubation lasts 22 to 29 days. The precocial young are cared for by both sexes but the young feed themselves. Fledging occurs after 28 to 35 days. (Ehrlich, et al., 1988; Nethersole-Thompson, 1986)

Home Range

We do not have information on home range for this species at this time.

Communication and Perception

American avocets make loud "wheet" or "pleeet" and shrill "kleeap" sounds that are often repeated. They are very noisy when intruders approach active nests. They also communicate using complex displays that include dancing, bowing and crouching. (Ehrlich, et al., 1988; Kaufman, 2000; Soothill and Soothill, 1982)

Food Habits

American avocets swoop their open bills back and forth in shallow water to catch aquatic insects. They may feed in flocks of up to 100 plus birds, in deep water they will "tip up" like dabbling ducks and are reportedly good swimmers.

Predation

American avocets are mostly quiet and uncaring but become extremely aggressive on breeding and nesting grounds and protest loudly and dive bomb when intruders approach. They have few non-human predators, some known nest predators include skunks (subfamily Mephitinae) and foxes (family Canidae). (Kaufman, 2000; Soothill and Soothill, 1982)

Ecosystem Roles

American avocets are important members of their ecosystem; because of their food habits they likely have a regulatory influence on insect and crustacean populations, and they are an important food source for their predators. They also have an influence on the plants and seeds they eat. (Brown, 1999; Brown, 1999)

Economic Importance for Humans: Positive

American avocets are enjoyable to watch and are sought out by many birders.

Economic Importance for Humans: Negative

There are no known adverse affects of American avocets on humans.

Conservation Status

Currently protected by the US Migratory Bird Act, American avocets are making a comeback after over-hunting in the 19th and early 20th centuries. The main threats to American avocets today are habitat loss and degredation. (Brown, 1999)

Other Comments

American avocets are very beautiful birds with personality! I worked near them at wetland and they are very vocal and protective of nests. It is interesting to watch them wade and feed in shallows.

Contributors

Alaine Camfield (editor), Animal Diversity Web.

Patina Thompson (author), University of Arizona, Todd McWhorter (editor), University of Arizona.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

Neotropical

living in the southern part of the New World. In other words, Central and South America.

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

brackish water

areas with salty water, usually in coastal marshes and estuaries.

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

crepuscular

active at dawn and dusk

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

fertilization

union of egg and spermatozoan

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

marsh

marshes are wetland areas often dominated by grasses and reeds.

migratory

makes seasonal movements between breeding and wintering grounds

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

omnivore

an animal that mainly eats all kinds of things, including plants and animals

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

seasonal breeding

breeding is confined to a particular season

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

swamp

a wetland area that may be permanently or intermittently covered in water, often dominated by woody vegetation.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

young precocial

young are relatively well-developed when born

References

Alden, P. 1999. National Audubon Society, Field Guide to the Southwestern States 1st Edition. New York: Random House.

Disclaimer:
The Animal Diversity Web is an educational resource written largely by and for college students. ADW doesn't cover all species in the world, nor does it include all the latest scientific information about organisms we describe. Though we edit our accounts for accuracy, we cannot guarantee all information in those accounts. While ADW staff and contributors provide references to books and websites that we believe are reputable, we cannot necessarily endorse the contents of references beyond our control.

This material is based upon work supported by the
National Science Foundation
Grants DRL 0089283, DRL 0628151, DUE 0633095, DRL 0918590, and DUE 1122742. Additional support has come from the Marisla Foundation, UM College of Literature, Science, and the Arts, Museum of Zoology, and Information and Technology Services.